Internal combustion engine ignition system

ABSTRACT

An apparatus for electrically controlling the spark advance of selected cylinders of a multicylinder engine so that the spark of the selected cylinders is advanced beyond others of the cylinders. For example, the selected cylinders may be advanced beyond normal operational advance to increase combustion chamber temperatures and pressures for a relatively short period so as to clean the surfaces of the combustion chamber. The cylinders which are advanced are changed in sequence or at random so that all of the cylinders are cleaned. The system may also be used to control the spark advance of the cylinders to provide differing advances for the respective cylinders to accommodate differences in operational conditions at the cylinders.

This is a continuation application of U.S. patent application Ser. No.651,042, filed Sept. 14, 1984, now abandoned which is a continuation ofSer. No. 374,803 filed May 4, 1982, now U.S. Pat. No 9,471,737, isusedSept. 18, 1984,continuation of Ser. No. 161,282, filed June 20, 1980,now abandoned, which is a division of application Ser. No. 934,322,filed Aug. 16, 1978, now U.S. Pat. No. 4,257,373, issued Mar. 24, 1981,which is a division of application Ser. No. 800,959, filed May 26, 1977,now U.S. Pat. No. 4,116,173, issued Sept. 26, 1978, which is acontinuation of Ser. No. 572,167, filed Apr. 28, 1975, now abandoned,which in turn is a division of Ser. No. 336,559, filed Feb. 28, 1973,now U.S. Pat. No. 3,903,856, issued Sept. 9, 1975.

BACKGROUND AND SUMMARY OF THE INVENTION

In recent years, scientists and the public generally have become moreaccutely aware of the injurious effects of air pollution, andadditionally, the contribution of the exhaust emissions of internalcombustion engines to air pollution. Consequently, legislation ofincreasing restrictiveness has been passed to limit the exhaustemissions from automobiles. Although the automobile engine manufactureshave attained a certain degree of success in meeting these exhaustemission restrictions, it has been found in tests that an automobilewhich has met the requirements at the time of manufacture, often may notmeet the requirements after only a relatively short period of use. Theexpectancy that an automobile engine will meet the restrictiverequirements diminishes with random, and often non-existent, maintenanceefforts by the owners. Clearly, laxity of owner maintenance is in largepart the result of the inconvenience connected with servicing of anautomobile, prolonged waiting, and often, the deprivation of the use ofthe automobile. Without mandatory legislation regarding automobilemaintenance, it is not expected that the maintenance efforts ofautomobile owners will significantly improve in the future.Consequently, the problem of maintaining an automobile engine in a lowemissions condition after manufacture of the engine is a particularlyperplexing one.

It is known that hydrocarbon emissions from the exhaust of automobileengines are in part the result of the existance of crevices in thecombustion chamber where gasoline, liquid and vapor may find refuge fromthe burning process so that they are released to the atmosphere duringthe exhaust stroke as unburned hydrocarbons. Internal combustion engineswhich are not properly maintained develop deposits in the combustionchamber which greatly increase the number and size of crevices. To alesser extent, a properly maintained engine will also develop depositsin the combustion chamber which results in increased unburnedhydrocarbons.

The present invention provides a system for cleaning the combustionchambers to reduce the combustion chamber deposits in a manner whichcauses minimal, if any, inconvenience to the owner of the automobile,and which improves the operation of the engine so that the owner will beinclined to use the system. The system may be vehicle-mounted, and ifdesired, can be made automatic in operation so that no attention fromthe owner or user is required. Alternatively, an engine cleaning systemaccording to the present invention can be adapted for use as a servicestation appliance, for example, by providing cooperating electricalfittings on the appliance and the automobile.

In one form of this invention, the ignition timing of selected cylindersof a multi-cylinder automobile engine is electrically advanced beyondthe ordinary operating advances, and preferably, to such a degree tochange the selected cylinders from power producers to power absorbers.The severe advance to those cylinders results in especially highcombustion chamber surface temperatures and high detonation pressureswhich serve to burn and dislodge the combustion chamber deposits so thatthey are removed from the combustion chamber on the exhaust stroke.Since some of the cylinders operate as power absorbers, the throttle canbe opened significantly above idle position so as to contribute to thehigh temperature and detonation pressures in the pre-ignited cylinders.By virtue of this feature, cleaning with advanced throttle opening canbe accomplished with the transmission of the vehicle in neutral ordisengaged from the engine without the use of a dynamometer or otherpower-absorbing device so that this system is especially adaptable toinstallation in the vehicle. Also, the period of operation is short sothat the high temperatures are limited to the combustion chambersurfaces whereby the underlying material is not damaged by overheating.The selected cylinders which are advanced are changed at random or insequence, automatically or manually, until all of the cylinders of theengine have been cleaned.

In one exemplary embodiment of a cleaning device of the presentinvention, a pulse derived from the automobile distributor contacts isreceived by a variable delay circuit which, in effect, provides anoutput pulse which may be variably advanced with respect to the ignitionof the next cylinder. With four-cylinder systems conventionaldistributors and coils may be used since almost 90° of supplementaryadvance is available which is adequate to cause the high surfacetemperatures and detonation pressures required for short periodcleaning. In the case of engines having more than four cylinders, suchas eight cylinder engines, the conventional distributor cap and coil ispreferably substituted by an electronic distributor to provide thepreferred degree of ignition advance.

Each of the systems disclosed herein may be readily modified toaccommodate differing advances for the various cylinders to accommodatevariations in fuel/air mixtures received by the cylinders. For example,the various cylinders may be adjusted in unison according to a singlefuel air mixture signal, or the advance of the individual cylinders maybe adjusted independently in accordance with plural fuel air mixturesignals for respective ones or groups of the cylinders.

In yet another exemplary system, the occurrence of detonation or"pinging" is sensed and the advance of the particular cylindersexperiencing detonation is retarded a fixed increment for eachoccurrence of detonation. When detonation is no longer detected at thatcylinder, the timing of that cylinder is allowed to advance at arelatively slow rate until the next occurrence of detonation.

In another exemplary system, the time of flame propogation from thespark plug to a preestablished location in the cylinder combustionchamber is measured and the advance of the particular cylinder is set inaccordance with the speed of propogation of the combustion flamerelative to the engine cycle. It will be appreciated that each of thetwo latter systems are fully adapted to the conditions which affectengine operation, for example, the octane of the fuel being used, enginetemperature and engine load.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a first exemplary embodiment of anignition system according to this invention which is especially suitablefor use with engines having four or less cylinders;

FIG. 2 is a series of charts illustrating the various signal sequencesof the system of FIG. 1;

FIG. 3 is a second exemplary embodiment of an ignition system accordingto the present invention which is especially suitable for mounting in avehicle having more than four cylinders;

FIG. 4 is a third exemplary embodiment of an ignition system accordingto the present invention which is especially suitable for use in aservice station or the like for periodic servicing of vehicles nothaving vehicle-mounted cleaning systems;

FIG. 5 is a fourth exemplary embodiment of an ignition system accordingto the present invention which is along the lines of the embodiment ofFIG. 3 but provides independent rates of advance for each of thecylinders of the engine;

FIG. 6 is a fifth exemplary embodiment of an ignition system accordingto the present invention which adjusts the ignition timing of each ofthe cylinders in accordance with detected detonations at each of thecylinders; and

FIG. 7 is a sixth exemplary embodiment of an ignition system accordingto the present invention which adjusts the ignition timing of each ofthe cylinders in accordance with the rate of flame propogation in eachof the cylinders relative to the engine cycle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a system 10 is illustrated which is especially suitable foruse with four cylinder internal combustion engines and which uses theconventional mechanical distributor and coil 12 of the engine. In thediscussion of the system 10, reference should be made to FIG. 2 in whichthe relationship of the various signals are graphically illustrated. Thesystem 10 receives the pulse 14 created upon opening of the automobiledistributor contacts 16 which disconnects the contact terminal 18 fromground so that the potential at the terminal 18 increases rapidly towardbattery potential. The pulse 14 is received by a first one-shotmultivibrator 20 which is triggered when the potential of pulse 14reaches the trigger level of the first one-shot multivibrator 20. Thefirst one-shot multivibrator provides a positive going pulse 22 on line26 and a negative going pulse 24 on line 28. The pulse 22 on line 26 isreceived by a tachometer 30 which time-averages the pulses to indicateengine speed and by a second one-shot multivibrator 32 which provides apositive going pulse 34 on line 36 and a negative going pulse 38 on line40. The negative going pulse 38 on line 40 is received by a thirdone-shot multivibrator 42 from line 44 which provides a single positivegoing pulse 46 on line 48. With particular reference to FIG. 2, it willbe noted that the pulse 46 is offset or delayed with respect to theother pulses 22, 24, 34 and 38 by the width of the pulse 38 since thethird one-shot multivibrator 42 responds to the positive going portionof the pulse 38. The pulse 46 is received by a switch 50 which keys asawtooth generator 54 so as to initiate a voltage ramp 52 from thesawtooth generator 54 which is delivered on a line 56 to the input of asample and hold circuit 58. The negative going pulse 38 on line 40 isdelivered to the gating terminal of the sample and hold circuit 58whereby the sample and hold circuit will provide an output on outputterminal 60 which is representative of the ramp voltage at the time thatthe sample and hold circuit 58 is gated. Recalling now that the pulse 38slightly precedes the pulse 46 which initiates the sawtooth generatorramp 52, it can be seen that the output of the sample and hold circuit58 will be near the maximum voltage of the sawtooth ramp 52.Consequently, the output on line 60 will be substantially representativeof the maximum potential of the sawtooth. The output on line 60 isreceived by a variable potentiometer 62 which is connected to groundthrough a switch 64. The potentiometer 62 has a wiper 66 which providesan output signal 68 on line 70 which is some fraction or portion of theoutput signal at output terminal 60, determined in accordance with theposition of the wiper 66, during intervals while the switch 64 isclosed. As will be appreciated hereinafter, the position of the wiper 66of the potentiometer 62, and therefore, the potential at wiper 66,determines the degree of supplementary advance of the cylinders selectedfor preignition. At times when the switch 64 is open, the signal 68 online 70 approaches the full potential signal at output terminal 60. Theswitch 64 is operated by a gating signal on line 72 which gating signalis present for 180 crank angle degrees preceding the normal firing timeof each of the cylinders to be advanced. A signal 68 on line 70 havingminimum potential level, as shown in FIG. 1, representative of thedegree of supplementary advance and the sawtooth signal 52 on a line 74which extends from line 56 are received at the input of a comparator 76.As illustrated in FIG. 2 the comparator 76 provides an output signal online 78 with the positive going leading edge thereof indicating when thepotential of the sawtooth wave equals the minimum potential of thedegree of advance signal 68. The output signal on line 78 is deliveredthrough a diode 80 to a last one-shot multivibrator 82 so as to providean output pulse on line 84 which is amplified by a buffer amplifier 86and is used to trigger a capacitive-discharge ignition system 88 whichsupplies an appropriate current pulse to the coil 12 to fire the sparkplug of the advanced cylinder. For the cylinders which are not advanced,the pulses 34 on line 36 are delivered through a diode 90 to the lastone-shot multivibrator 82 to operate the capacitive-discharge ignitionsystem 88 to fire the spark plugs of the cylinders with substantiallynormal advance.

The cylinders to be supplementarily advanced are selected by operationof one or more of a plurality of switches 92 of a selector system 94,with one switch being associated with each cylinder. The switches 92 forthe cylinders 1-4 may be either manually set or may be automatically setby an automatic control 93.

For example, automatic initiation of the cleaning operation by thecontrol 93 can be conditioned upon the elapse of a preselected period oftime, the operation of a vehicle in which the engine is mounted for apredetermined distance as can be determined from an odometer, or thepreselected number of engine revolutions. The automatic control 93should be programmed so that cleaning occurs only when full power fromthe engine is not required. For example, in an automobile installation,selected cylinders may be advanced while the engine is providingcruising power or less, and means may be provided to turn the system offto return the advance to normal when a demand for additional power ismade such as during passing or an emergency maneuver so that the systemdoes not limit the power available from the engine under thoseconditions. The demand for additional power may be sensed in accordancewith accelerator position or manifold pressure. As an alternative tofully automatic operation, an automatic indicator system may be utilizedand the driver may be relied upon to switch on the cleaning system at aconvenient time. In this regard, the usual method of indication may beused such as indicator lights, buzzers, etc. Although the switches 92are not shown to be mechanically operated by the automatic control 93they may be readily operated by transistors, SCR's, electromagneticrelays, etc. The selector system 94 provides gating pulses on line 72which are timed so as to be present for intervals preceding the normalfiring times of the cylinders to be advanced. The selecting circuit 94uses a first flip-flop 96 which receives the pulses 24 on line 28, and asecond flip-flop which receives the "one" output of the first flip-flop96 so as to provide a count of the pulses 24 in a binary code form in aknown manner. Decoder diode matrix 100 receives the outputs of the firstand second flip-flops 96 and 98 and converts the binary code in a knownmanner to provide sequentially occurring, substantially contiguouspulses on detector output lines 102, 104, 106 and 108 representing the2nd, 3rd, 4th and 1st cylinders, respectively in the engine firingorder. Closing of switch 92 corresponding to a selected cylindertransmits the pulses from the respective one of the output lines 102-108to the switch 64 so as to gate the switch 64 and select the cylinderhaving the closed switch for supplementary advance. If the identity ofthe advanced cylinders is desired the switch sequence 2, 3, 4, 1 may becorrectly superimposed on the engine firing order sequence by anidentifying apparatus 110 which includes a capacitive pickup clip 112which, with switch #1 open is clipped to #1 cylinder high voltage sparkplug wire so as to identify the rotative position of the engine withrespect to the firing periods of the cylinders. In the illustratedexample, the pickup clip provides a signal on a pickup output line 114at the normal ignition time of #1 cylinder. The signal on line 114 isdelivered to a coincidence detector and bulb driver 116 which alsoreceives a signal from line 102 on line 118 which commences at thenormal firing time of cylinder #1 which is provided by the detector anddiode matrix 100. Upon coincidence of the signals on line 114 and line118, the coincidence detector and bulb driver 116 provide an appropriatepotential to light a lamp 120. Consequently, while synchronization isestablished between the selected crankshaft rotational position and thegeneration of a pulse corresponding to the selected rotational positionof the crankshaft, the synchronizing lamp 120 will be lit. Synchronismis initially established by closing a switch 122 which resets flip-flops96 and 98 to provide an output pulse for switch #2 when the properrotative position of the crankshaft for firing is detected by thecapacitive pickup clip 112. Switch #2 then controls the pulse initiatedby the normal firing time of cylinder #1 so as to insure either thepresence or absence of supplementary advance to the second cylinder inthe firing order. Thereafter, synchronism is maintained although theswitch 122 is disconnected through counting of the occurrences ofdistributor contact opening.

In summary of the operation of the system 10, the opening of the points16 provides a pulse 14 which is used to control the firing of theadvanced as well as the non-advanced cylinders. Considering a cylinderwhich is not supplementarily advanced as indicated by an open switch 92for that cylinder the pulse 14 is effective through intermediateone-shot multivibrators 20 and 32 to initiate an output pulse from thelast one-shot multivibrator 82 which is received by the capacitivedischarge system 88. The capacitive discharge system 88 in turn firesthe appropriate spark plug by generating a current pulse in the primaryof the coil 12 at a time appropriate to the respective cylinder.Considering now a cylinder which is supplementarily advanced, it will beseen that the pulse 14 correlative to the preceding cylinder yields apulse on line 78 which is variably delayed in accordance with theadjustment of the potentiometer 62 so that the pulse 34 on line 36correlative to the cylinder under a non-advanced condition which wouldordinarily be effective to operate the capacitive discharge ignitionsystem 88 to fire the cylinder is preceded and pre-empted by a pulse online 78 from the comparator 76 to preignite the cylinder. Moreparticularly, a sawtooth wave is generated at generator 59 which iscompared to a signal 68 representing a fraction of the sawtooth peakwhich fraction is established in accordance with the desiredsupplementary advance. When the sawtooth wave exceeds the minimumpotential of the supplementary advance signal 68, an output signal online 78 is provided which is effective to operate the capacitordischarge ignition system 88. It will be appreciated that increasinglypositive signals 68 result in longer delays from the preceding pulse,and therefore, shorter supplementary advances.

To accomplish cleaning of the advanced cylinders, the ignitionsupplementary advance is severe enough, preferably almost 90 degrees ofcrank shaft angle, to result in an especially high combustion chambersurface temperatures and high detonation pressures to burn and dislodgethe combustion chamber deposits. Preferably, in a four cylinder engine,two of the cylinders are operated in that manner whereby they serve aspower absorbers and so that the throttle can be opened significantlyabove idle position to contribute to the cleaning effect. When thesystem is being used to advance selected cylinders to accommodatedifferences in fuel to air mixtures, the total ignition advance is muchless severe and is normally in the range of from 10 to 40 degrees beforetop dead center.

In FIG. 3, an ignition system 124 is illustrated which is adapted toprovide an electronically controlled ignition advance for ordinaryoperation of the vehicle. Additionally, the system 124 of FIG. 3 isreadily adaptable for providing supplementary advance for selectedcylinders for cleaning generally as set forth above. The system 124senses a pulse 14 upon an opening of the contacts 16, and, for thisembodiment, there is one such opening event for each cam shaftrevolution. The pulse 14 is received by a first one-shot multivibrator126 which provides a negative going pulse on line 128 when the gatingthreshold of the first one-shot multivibrator 126 is reached. Thenegative going pulse on line 128 is received by a second one-shotmultivibrator 130 which provides a positive going output pulse on line132 in response to the positive going portion of the pulse on line 128so that the pulse on line 132 is delayed for time equal to the width ofthe pulse on line 128. The pulse on line 132 is received by switch 134which is effective to reset to zero volts the output of a sawtoothgenerator 136 upon closing of the switch 134. Consequently, a sawtoothwaveform is provided on output line 138 of sawtooth generator 136 whichrepeats on each occurrence of an output pulse from the one-shotmultivibrator 130 on line 132. A sawtooth peak sample and hold circuit140 receives the sawtooth waveform on line 138 and a negative goingpulse on line 128 from line 141 so as to provide an output on line 144substantially representative of the peak potential of the sawtoothwaveform on line 138, as described with respect to FIGS. 1 and 2. Thesignal on line 144 is received by a circular voltage divider network 142comprising variable resistors R1, R8, R4, R3, R6, R5, R7 and R2 havingpreselected resistive values which establish the advance of cylinders 1,8, 4, 3, 6, 5, 7 and 2, respectively, so that differences in optimumspark advance which are treated as being invariant with engine operatingparameters can be accommodated. One or more of the resistors may haveresistive values differing from the one or more of the others.Alternatively, or in combination, resistor wiper contacts C1, C8, C4,C3, C6, C5, C7 and C2 may be positionally adjustable so as to vary theresistive values of the respective resistors R1-R8. When the wipercontacts C1-C8 are in the positions shown, the ignition timing isestablished for normal operation of the engine with constant differencesin optimum spark advance being accommodated by the diverse values.However, one or more selected cylinders may be supplementarily advancedto clean the selected cylinders by switching the respective wipercontact C1-C8 counterclockwise on the voltage divider network 142 tochange the voltage seen by the respective wiper contact C1-C8, toproduce earlier intersection with the modified sawtooth train on line152 as will be better appreciated hereinafter. It will be noted thatduring operation with wipers as illustrated, the potential at wipercontact C1 is always greater than at wiper contact C8, the potential atwiper C8 is always less than that at any other wiper contact. Thepotential at each of the contacts C1-C8 is delivered to one terminal ofa voltage comparator for the respective cylinder, and particularly, thepotential at C1 is delivered to one terminal of a first cylindercomparator, the potential at contact C8 is delivered to an eighthcylinder comparator, etc.

The sawtooth signals on line 138 are received at one terminal of adifferential operational amplifier 146 via a line 148. The otherterminal of the differential operational amplifier 146 receives a signalon line 150 which is representative of one or more engine operatingparameters according to which ignition advance is to be varied, such asengine speed, engine demand as indicated by throttle angle or manifoldpressure, and/or fuel octane. Accordingly, the differential operationalamplifier 146 provides a modified sawtooth output signal on line 152which is representative of the difference between the sawtooth generatoroutput waveform on line 138 and the signal on line 150 representative ofthe engine operating parameters. The signal on line 152 is received bythe other input terminals of each of the first through eighth cylindercomparators whereby the sawtooth waveform, as modified by engineoperating parameters, will be compared with the potentials at therespective wiper contacts C1-C8.

It should be noted, that, in the embodiment illustrated, the magnitudeof the voltage on line 150 may be no larger than approximately oneeighth of the magnitude of the voltage on line 144. Otherwise, themaximum amplitude of the modified sawtooth output of amplifier 146 maybe below the fraction of the unmodified sawtooth peak picked off thevoltage divider by wiper C1 thus preventing an intersection in thecomparator for cylinder #1. Thus it will be recognized that increasingthe voltage on line 150 has substantially the same effect on thecomparator output as moving contacts C1-C8 clockwise on the voltagedivider. Each of the cylinder comparators provides an output signal toan associated one-shot multivibrator and buffer amplifier when thesignal of the modified sawtooth waveform on line 152 reaches the voltageat the associated wiper contact. Since the potential at wiper contact C8is closest to zero, i.e. ground potential, the number eight cylindercomparator provides an output signal near the inception or zero point ofthe sawtooth waveform. In sequence, the cylinder comparators forcylinders 8, 4, 3, 6, 5, 7, 2 and 1, respectively, provide outputsignals when the modified sawtooth waveform equals or exceeds thevoltage at its respective wiper contact. The entire voltage dividernetwork 142 represents 720° of crankshaft revolution. The one-shotbuffers for cylinders 1-8 are effective to drive silicon controlledrectifiers Q1-Q8, respectively, into conduction so as to connect thecapacitive discharge system 154 through respective ones of ignitioncoils T1-T8 which are connected to fire spark plugs P1-P8, respectively.Separate coils are utilized for each spark plug so as to dispense with aconventional mechanical distributor for eight cylinder engines whichwould limit the system to a supplementary ignition advance of only 45°.More particularly, it will be appreciated that with mechanicaldistributors, advances of more than 45° will position the rotor armcloser to the contact of the preceding cylinder to be fired than thecontact of the intended cylinder so as to cause flash-over to thepreceding contact. It is desirable for efficient cleaning of the engineto establish ignition advances of more than 45°. It will also beappreciated that conventional mechanical distributors may be used withfour cylinder engines as illustrated in FIG. 1 since the fewer number ofcyliders permit advances of approximately 90° without flash-over.

The signal on line 150 representative of engine operating parameters isderived from a function generator 156 which receives a signalrepresentative of the peak potential of the sawtooth waveform from line144 on a line 158. Since the peak potential is representative of thetime elapse between pulses 14, it is inversely representative of, i.e.the reciprocal of, engine speed. The function generator also receives asignal from a variable potentiometer 160 which is representative ofthrottle opening or manifold pressure. The potentiometer 160 may includea wiper contact 162 which is connected to the throttle arm of thecarburetor so as to provide a fractional amount of a regulated voltagewhich is varied in accordance with throttle position. A filter capacitor164 is connected between the wiper contact and ground so that thegenerator may be delayed in its response to rapid and brief changes inthrottle position. The function generator also includes a manual input166 which suitably adjusts the ignition advance in accordance with theoctane of the fuel being used by the automobile. The contribution ofeach of engine speed, throttle position, and octane to the signal online 150 may be selected in accordance with known relationships so as toprovide an appropriate engine operating parameter signal on line 150.

It will be appreciated that the sawtooth peak signal on line 144 couldhave been modulated in accordance with engine operating parametersrather than the sawtooth waveform. It will also be appreciated that theadjustment of the wiper contacts C1-C8 can be made manually by theoperator, or may be accomplished by a mechanical or electronic controlas described with respect to FIG. 1.

In summary of the operation of the ignition system 124, the occurrenceof a pulse 14 representing the opening of contacts 16 initiates asawtooth waveform on line 138 after a preset very small time delay. Thesawtooth waveform on line 138 is modified in accordance with selectedengine operational conditions at operational amplifier 146. A signalrepresentative of the peak of the sawtooth waveform, provided by thesample and hold circuit 140, is reduced in potential level in stages inaccordance with the desired advance for each cylinder and the timesequence of firing of each cylinder by the voltage divider 142. Themodified waveform from the operational amplifier 146 is compared at eachcylinder with the potential derived from the voltage divider network 142so as to yield a spark initiating signal when the modified waveform fromthe operational amplifier exceeds the potential from the voltage divider142 whereby each spark plug P1-P8 is fired in turn and with apreselected advance to accommodate differing engine operating parameterssuch as fuel/air mixtures and/or to accomplish combustion chambercleaning.

In FIG. 4, an ignition appliance 168 is shown which is suitable for usein service stations and the like for cleaning internal combustionengines of automobiles brought in for servicing. The appliance 168includes means 170 sensitive to the rotational position of thedistributor shaft which, for example, may include a pickup 172 which iscapacitatively coupled to an ignition wire such as a #1 spark plug wireas shown to detect the transmission of a potential pulse through thewire. The pulse which is coupled to the capacitive pickup 172 isreceived by a cold cathode tube 174 to fire the tube thereby emittinglight. A photo-transistor 176 is optically coupled to the tube so thatthe transistor 176 is turned on when the tube 174 is fired. When thetransistor 176 is off, its collector 178 is near battery potential whilethe firing of the transistor 176 pulls the collector potential to nearground potential so as to create a negative going pulse. The thuslycreated negative going pulse is delivered to an amplifying transistor180 which is turned on when the negative going pulse is received so asto provide a positive going pulse at its collector 182 which isdelivered to a third amplifying transistor 184 to turn on transistor 184to provide a negative going pulse at its collector 186. The negativegoing pulse at the collector of the transistor 184 is delivered to afirst one-shot multivibrator 188 which provides a negative going pulseof predetermined width to a second one-shot multivibrator 190 and to thegating terminal of a sawtooth sample and hold circuit 192. The sawtoothsample and hold circuit 192 is gated on the positive going portion ofthe pulse from the first one-shot multivibrator 188. The second one-shotmultivibrator 190 is responsive to the positive going portion of thepulse from the first one-shot multivibrator 188 to provide a positivegoing pulse which is delivered to an electronic switch 194 which isoperatively connected to a sawtooth generator 196 to reset the sawtoothgenerator 196 on each occurrence of the pulse from the one-shotmultivibrator 190. The sawtooth genertor 196 provides a sawtoothwaveform on line 198 which is delivered to the sample terminal of thesawtooth peak sample and hold circuit 192. The sawtooth peak sample andhold circuit is gated by the negative going portion of the pulse fromthe first one-shot multivibrator 188 so that the sawtooth peak sampleand hold circuit holds the value of the sawtooth wave slightly prior toresetting of the sawtooth generator, and particularly, at a timeinterval prior to resetting of the sawtooth generator 196 equal to thewidth of the pulse from the first one-shot multivibrator 188.Accordingly, the signal held by the sawtooth peak sample and holdcircuit 192 is substantially representative of the peak of the sawtoothwaveform generated by the sawtooth generator 196. The sawtooth peaksignal of the sawtooth peak sample and hold circuit 192 is received by acircular voltage divider network 200 having terminals T1-T8 forcylinders 1 through 8, respectively, which are adapted to be engaged bywiper contact C1-C8, respectively, so as to provide normal ignitiontiming. Accordingly, the values of the resistances intermediate theterminals T1-T8 are of equal value. The wiper contacts C1-C8 are adaptedto be positionable intermediate the terminals T1-T8 toward the nextpreceding terminal cylinder in the firing order (counterclockwise) so asto supplement the advance of the selected cylinders. With regard to FIG.4, it can be seen that the wiper contact C4 for cylinder four isadvanced approximately midway between the terminals T4 and T8 so as toprovide approximately 45° supplemental ignition advance while the wipercontact C3 for cylinder three is advanced to contact T4 to provide 90°supplemental advance. Terminals T1 and T1' are separated in voltage bythe prevailing sawtooth amplitude and may be considered to be separatedin time by the very small duration of the negative going pulse from thefirst one-shot multivibrator 188. Thus contact C8, for example, may bemoved counter-clockwise beyond T1 in the event it is desired tosupplement the advance of cylinder #8 more than 90 crankshaft degrees.The potentials at wiper contacts C1-C8 are compared with the sawtoothwaveform from the sawtooth generator 196 at the first through eighthcylinder comparators to yield output signals therefrom when the signalsare equal. The output signals from the first through eighth cylindercomparators are delivered to one-shot buffers which provide a pulse tofire silicon controlled rectifiers Q1-Q8, respectively, which in turndeliver a primary ignition pulse from a capacitive discharge system 202to ignition coils T1-T8 for spark plugs P1-P8, as previously describedwith respect to the system of FIG. 3.

It will be appreciated that the appliance 168 of FIG. 4 is readilyadapted for service station use since it is readily connectable to anautomobile engine. More particularly, the appliance 168 can beoperatively connected to an automobile engine by removal of all of theplug leads, clamping the capacitive pickup clip 172 to the appropriatedistributor lead, and plugging leads from the ignition coils T1-T8 tothe respective spark plugs P1-P8. Selected ones of the cylinders 1through 8 may be advanced by adjustment of the wiper contacts C1-C8 aspreviously described. If desired, cooperating electrical fittings may beinstalled on the appliance and on the automobile so that the abovedescribed connections and disconnections may be made in a singleoperation.

In FIG. 5, another exemplary embodiment of an ignition system 202according to the present invention is illustrated. The ignition system202 of FIG. 5 is like the ignition system 124 of FIG. 3 in that itincludes means for providing a sawtooth waveform on line 148 whichrepeats on each mechanical cycle of the automobile engine, i.e., each720° of rotation of the crankshaft of a four cycle piston engine. Thesystem 202 also includes means for providing a signal on line 144representative of the inverse of engine speed. The sawtooth is phasedsuch that the ramp of the sawtooth waveform is initiated previously tothe most advanced ignition timing contemplated for the cylinder 8, andmay be established in accordance with the opening of conventionaldistributor contacts for the engine. For example, the initiation of theramp may occur on compression stroke top dead center for cylinder #1.Terminals T1-T8 corresponding to cylinders 1-8 are spaced about avoltage dividing resistor 204 in the quarter appropriate for firing, forexample, T8, T4, T3, T6, T5, T7, T2, T1, respectively, as illustrated.The terminals T1-T8 may be equally spaced about the voltage dividingresistor 204, or alternatively, certain of the terminals T1-T8 may beforwardly or rearwardly in position to advance or retard the firing ofthe selected cylinders. It will be appreciated that this advance orretradation by virtue of the adjustment of the position of the selectedterminals will introduce a bias in the spark advance of the particularcylinders. By way of illustration, the bias of the selected cylindersmay be established so that four cylinders of an eight cylinder enginemay run on propane and four cylinders of the engine may run on gasoline.The terminals T1-T8 may be manually or automatically adjustable tointroduce the desired bias. Consequently, ignition timing may be variedindependently or collectively for the cylinders of the engine. In theparticular example shown, adjustment of the terminals T1-T8 in theclockwise direction increases the voltage level at that terminal toretard the spark, and vice-versa. In this regard, a clockwise movementfrom the terminal T8 is in the direction of increasing voltage, while aclockwise movement from each of the other terminals is in the directionof decreasing voltage. Nonetheless, the effect of the clockwise movementis the same in each case, i.e. to advance the spark since the movementfrom the terminal T8 past the terminal connecting with line 144represents only a small movement in crank angle although the potentialdifference may be quite large. More specifically, the rotation of crankangle representative of the movement of the terminal T8 to the terminalconnecting with line 144 represents the crank angle rotation during thewidth of the pulse from the first one-shot multivibrator 126.

As described with respect to FIG. 3, the terminals T1-T8 are connectedto first through eight cylinder comparators 206 as illustrated in FIG.5. The signal on line 144 representative of the inverse of the enginespeed is also connected to first through eighth cylinder functiongenerators indicated at 208. The first through eighth cylinder functiongenerators 208 also receive a signal representative of engine octanefrom an octane selector potentiometer 210 which is manually adjustableby the vehicle operator and is preferably located in the passengercompartment of the vehicle, and a signal representative of chargedensity from a charge density potentiometer 162 which is preferablyoperatively connected to the engine throttle for responding to theengine throttle or to a pressure transducer to respond to intakemanifold pressure. The contribution of each of engine speed, throttleposition, and octane to the output signal from each function generator208 is established in accordance with known relationships so as toprovide an appropriate engine operating parameter signal to anassociated summing amplifier indicated at 210 for each cylinde. Each ofthe function generators 208 establish independent functionalrelationships based on the parameters of engine speed, octane and chargedensity in accordance with the variations in the design test performanceof the engine in response to those parameters for each cylinder. In thisregard, burning time within the combustion chambers of each cylinder isnot identical each with respect to the other, but rather, the combustiontime may vary due to several factors including the variations in thefuel air ratio between the cylinders. For example, the fuel air ratio ofa modern V8 engine may vary as much as two ratios between the richestcylinder and the leanest cylinder under certain conditions of speed andload. The function generators for each of the cylinders produces anoutput signal which provides an optimum spark advance for each cylinderby adjustment of each of the function generators in accordance with thepredictable variations between the cylinders.

The summing amplifiers 210, in addition to receiving the output signalfrom the function generators 208, also receives the sawtooth waveformfrom line 148. The summing amplifiers 210 also receive the output signalfrom the function generators 208 so that the output from the summingamplifier represents a sawtooth waveform which is modified in accordancewith the signal from the function generators 208, and particularly, isreduced in accordance with the signal from the function generators 208.The modified sawtooth waveform from the summing amplifiers 210 arecompared with the signals from the respective ones of the terminalsT1-T8 at associated comparators 206 for the first through eighthcylinders so as to fire an associated SCR when the signals are equal.The firing of the SCR discharges the capacitor of a CD system 214through individual ignition coils C1-C8 which in turn fire spark plugsP1-P8.

In FIG. 6, yet another exemplary embodiment of an ignition systemaccording to the present invention is shown. The ignition system 220 ofFIG. 6 is like the ignition system 202 of FIG. 5 and the ignition system124 of FIG. 3, and accordingly, signals of like nature from likecomponents are shown to be received on like-numbered conductors. Hence,a sigal is received on a line 144 representative of the peak amplitudeof the sawtooth waveform which is in turn inversely representative ofthe engine speed, a signal line 162 is received which is representativeof the charge density, a sawtooth waveform signal on line 148 isreceived which repeats on each mechanical cycle of the engine, i.e. each720° of rotation of the crankshaft of a four cycle piston engine, andsignals are received by comparators 206 for the respective cylinders ofthe engine from terminals T1-T8 on a voltage dividing resistor 204, allas previously described.

The ignition system 220 of FIG. 6 differs from the previously describedignition system in that the system 220 features closed loop control ofthe spark advance for each cylinder as a function of detectedundesirable detonations. More particularly, the ignition system of FIG.5 is capable of operating each of the combustion chambers of amulti-cylinder engine as close to a detonation condition as may bedesired without suffering significant power loss from detonation. Inthis regard, under engine operating conditions involving slow speed andhigh manifold pressure, the spark advance is frequently limited by earlyundesirable detonations. If detonation did not occur, more torque couldbe obtained by advancing the spark. Since there are variations inoperating conditions between the cylinders and variations in operatingconditions from cycle to cycle, all of which affect the spark advance atwhich detonation may occur for each of the cylinders, the traditionalmethod for avoiding undesirable detonation is to retard the spark to allof the cylinders until detonation is reduced to an acceptable level atall cylinders and under all cycle to cycle variations. In other words,the spark is sufficiently retarded so that the worst cylinder under theworst cyclic conditions is accommodated. Consequently, the cylinderswhich could tolerate an additional spark advance without undesirabledetonation are ignited subsequent to the optimum time, and therefore, donot provide optimum torque. In addition to the problem of accommodatingthe variations between cylinders and variations between cycles,variations in the octane rating of the fuel used during the life of anengine has been a problem. The system of FIG. 6 provides a solution tothe problem of variations between cylinders, variations from cycle tocycle, and variations in fuel automatically and effectively withoutattention from the operator.

To accomplish the above end, a transducer 222 is provided which isattached to the block of the engine, e.g. by threading into a tappedblind hole in the engine block, and which is responsive to vibrationstransmitted through the block which are representative of an undesirabledetonation. For example, the transducer 222 can be responsive to thevibrations in the audible range and preferably provides an electricaloutput signal representative thereof. The output signal of thetransducer 222 is amplified by a suitable amplifier 224 and isthereafter received by a bandpass filter and threshold device 226. Thebandpass filter and threshold device 226 allows the transmission of onlya very narrow band of frequencies detected by the transducer 222 andprovides an output signal when the frequencies at this narrow bandexceed a predetermined threshold. The narrow band is selected so as tobe within the range of frequencies which are distinctively related toundesirable detonations as opposed to frequencies caused by normalmechanical vibrations and normal charge burning. The threshold level ofthe threshold device is set so that the device will not pass signalscaused by spurious low magnitude vibrations due to effects notindicative of an undesirable detonation. The output of the bandpassfilter and threshold device 226 is provided to gates 228 for cylinders 1through 8 via a common conductor 230. The gates 228 receive the outputof the bandpass filter and threshold device 226 at one terminal and agating signal from the respective gates of the firing SCR's onrespective lines 232 for each of the cylinders 1-8, and a gate durationsignal from the line 144 via individual lines 234. The output of thegates 228 is provided to respective function generators 236 for thecylinders 1-8 by respective lines 238. The gates 228 transfer the signalfrom the bandpass filter and threshold device 226 representative of anundesirable detonation to the function generator 236 for a periodbeginning with the provision of a gating signal on the respective line232 having a duration established by the gate duration signal 234. Thegates 228 are used to time-isolate the post-ignition detonations foreach cylinder from the other cylinders so that the appropriate functiongenerator 236 can be controlled to adjust the timing of that cylinderonly. In this regard, it is known that, initially at least, anundesirable detonation for each cylinder will occur in the intervalbetween the provision of an ignition signal to the gate of the SCR forthat cylinder until a predetermined time thereafter which is inverselyproportional to the speed of the engine. That predetermined time isestablished by the gate duration signal on each line 234 which isinversely related to the speed of the engine as previously explained. Ifdesired, the predetermined period in which an undesirable detonation fora cylinder can occur can alternatively be established by opening thegate for that cylinder in the interval between the provision of anignition signal to the SCR for that cylinder and the provision of anignition signal to the SCR of the next cylinder to be fired. In thelatter method, the gate would be inhibited by the gating signal to theSCR of the next cylinder to be fired.

The function generators 236 are responsive to the engine speed asobtained from line 144, the charge density as obtained from line 162,and pre-ignition detonation conditions as obtained from line 238. Thefunction generator 236 responds to charge density and engine speed,analogous to manifold vacuum and centrifugal mechanism signals ofconventional spark advance systems, respectively, in the mannerpreviously described. The output signal of the function generator 236provides an initial nominal spark advance setting in accordance withknown spark advance information. When an undesirable detonation isdetected as indicated by the receipt of a signal on line 238, thefunction generator provides a signal which is effective to decrease thespark advance a predetermined small increment. Each successive time thata signal on line 238 is received indicating that the respective cylinderis experiencing an undesirable detonation, the function generator outputretards the spark a like increment, for example, one degree for eachcycle. When the absence of a signal on line 238 indicates that therespective cylinder is not experiencing an undesirable detonation, thespark is automatically advanced a small degree, e.g. 0.01 degree foreach cycle, until such time that an undesirable detonation is detectedat which time the spark is again retarded the aforementioned increment.In this manner, the spark advance for each cylinder is subject tocontinuous adjustment in accordance with the burning conditions in thatcylinder so that the charge in each of the cylinders is ignited at theoptimum time. The function generator 236 controls the spark in themanner described with respect to the system 202 of FIG. 5 via summingamplifiers 212 and comparators 206 which control respective SCR's forthe cylinders. As previously described, the SCR's discharge thecapacitor of a capacitive discharge ignition system into respectiveignition coils C1-C8 for spark plugs P1-P8.

In FIG. 7, still another examplary embodiment of an ignition systemaccording to the present invention is illustrated. The ignition system240 of FIG. 7 is along the lines of the ignition system 220 of FIG. 6and also includes a closed loop control of spark advance as a functionof the burning conditions in each of the respective cylinders. In thesystem 240 of FIG. 7, the charge burning time in each of the cylindersis measured by measuring the time that the flame front takes to progressa predetermined distance and the advance for each of the cylinders isestablished according to the charge burning time for that cylinder. Inthis sense, the closed-loop system of FIG. 7 is responsive to theanalogue representation of charge burning time whereas the ignitionsystem 220 of FIG. 6 is responsive to a binary signal indicating whetheror not the cylinder is experiencing an undesirable detonation.

The system 240 receives the previously described signal representativeof the inverse of engine speed on line 144 and the sawtooth waveform online 148. For brevity, only a single cylinder of a multicylinder engineis illustrated in FIG. 7, however, it will be appreciated that anynumber of cylinders can be similarly controlled by duplication of thesystem shown as taught with respect to the previous embodiments.

In FIG. 7, cylinder head 242 of the engine is provided with anionization detector 244 which in essence includes a pair of spacedelectrodes projecting into the combustion chamber, and means formeasuring the electrical resistance therebetween. Upon ignition of thecombustible mixture in the cylinder 242 by the spark plug P1, a flamefront advances from the electrodes of the spark plug P1 to theelectrodes of the ionization detector 244, traversing the distance d.The time of this traverse is measured by a timing circuit 246 whichreceives a signal from the gate of the SCR when the SCR is fired andwhich receives a signal from the ionization detector 244 when theresistance between the electrodes of the ionization detector 244 hasdecreased to indicate that the flame has reached the ionization detector244. The timing circuit measures this interval in fractions of a secondand provides an analogue signal representative thereof on line 248 whichis received by a function generator 250. The function generator 250receives a signal from line 144 representative of the inverse of theengine speed in revolutions per minute and the analogue signalrepresentative of the time of flame propagation and provides a sparkadvance signal on line 252 to the previously described summing amplifier210 to establish the ignition advance for the cylinder.

Empirically, it has been found desirable to establish the spark advanceso that three-quarters of the burning time of the charge occurs beforetop dead center of the compression stroke. With a view towards achievingthis result, the following expression can be derived for the optimumspark advance.

    0.75KT=OSA/360×60/RPM

or

    OSA=4.5KT×RPM

where:

K=an empirical factor relating the measured time for the flame front toprogress the distance d between the spark plug P1 and the ionizationdetector 244 and the actual burning time for the charge in thecombustion chamber.

T=the actual measured time required for the flame front to traverse thedistance d from the spark plug P1 to the ionization detector 244.

OSA=optimum spark advance.

RPM=crankshaft revolutions per minute.

With regard to the above, the quantity OSA/360 represents the fractionof a revolution before top dead center during which burning occurs andthe quantity 60/RPM represents the time of each revolution in seconds.The signal on line 252 representative of the desired spark advance isprovided in accordance with the above relationship.

The summing amplifier 210 receives the sawtooth waveform on line 148 inaddition to the spark advance signal on line 252 and provides a signalrepresentative of the difference between the sawtooth waveform and thefunction generator output signal to a comparator 206 as previouslydescribed. Also, as previously described, the comparator 206 receives asignal from the terminal T1 of a voltage dividing resistor 204 and theperiodic signal from the summing amplifier 210 and provides an outputsignal to the gate of an SCR at the appropriate time for firing thespark plug P1 of the first cylinder. The SCR discharges a capacitor in aCD system (not shown) through a coil C1 for the first spark plug P1.

The ionization detector 244 should be located as remotely as practicalfrom the spark plug P1 so as to provide a long distance d so that thevelocity of the flame front can be measured with the greatest possibleaccuracy. Additionally, the possibility that certain detonations will beunrecognized is reduced. With regard to the latter, should a detonationoccur following firing of the spark plug P1, but before the flame frontreaches the ionization detector 244, the detonation condition will bereflected in a measurement of an increased flame velocity and the sparkadvance will be suitably adjusted to retard the spark. However, shoulddetonation occur subsequent to the time that the flame front reaches theionization detector 244, the detonation will not be detected since anoutput signal from the flame detector 244 will already have beenprovided. Since the severity of a detonation is a function of theparticipating charge quantity, detonations occurring after the flamefront passes the ionization detector 244, provided the ionizationdetector 244 is located as remotely from the spark plug P1 as possible,will be of a low order of severity and will not be consequential.

Although reference has been made to cylinders and cylinder chambersthroughout the description of the present invention, it will beappreciated that the term "cylinder" should be given broader meaning soas to apply to any structure providing a combustion chamber receving acharge which is ignited in accordance with a predetermined timing withrespect to an operating cycle. For example, the ignition timing of aWankel engine utilizing rotors and rotor chambers may be suitablycontrolled by the ignition systems of the present invention. Moreover,the term "top dead center" should be considered to be the time thatcontraction of the volume of a combustion chamber is terminated andexpansion of the volume of the combustion chamber is initiated.Additionally, although a sawtooth waveform is utilized as a signalhaving a value which monotonically varies with at least a definableportion of the operating cycle of an engine, any other waveform may beused which is appropriately indicative of the elapse of at least aportion of the operating cycle of an engine. The period of the waveformmay be established so as to be equal to a complete operational cycle ofthe engine, i.e. one in which all of the cylinders have been fired asdescribed with respect to the embodiments of FIGS. 3 and 4, or theperiod may be set to equal one or other integral number of therotational increments between corresponding piston positions ofsuccessively fired cylinders. For example, the period may be equal tothe rotational increment between the top-dead-center positions of thepistons for successively-fired cylinders, as described with respect tothe embodiment of FIG. 1. Alternatively, the period may be establishedto equal an integral number of these increments between top-dead-centerpositions of the pistons of successively-fired cylinders.

While it will be apparent that the teachings herein are well calculatedto teach one skilled in the art the method of making preferredembodiments of this invention, it will be appreciated that the inventionis susceptible to modification, variation and change without departingfrom the proper scope of meaning of the subjoined claims.

What is claimed is:
 1. In an engine having a predetermined operatingcycle and including wall means defining at least one combustion chamberand igniting means associated with said combustion chamber for ignitinga charge of fuel and air in said combustion chamber when energized, saidfuel having a predeterminable octane rating, an ignition system forcontrolling the timing of the ignition of said charge for saidcombustion chambers, comprising;energizing means adapted to be connectedto said igniting means for energizing said igniting means in response toa timing signal, means for generating a timing signal operativelyconnected to said energizing means, said timing signal being adjustablewith respect to the mechanical cycle of said engine in response to anengine speed parameter and a charge density parameter, a manuallyadjustable octane selector and, function generator means responsive tomanual actuation of said octane selector and operatively connected tosaid timing signal for selecting a predefined range of ignition timingrelationships in accordance with said predeterminable octane rating,said engine speed parameter and said charge density parameter such thatthe ignition timing adjustment due to said predeterminable octanerating, said engine speed parameter and said charge density parameter ismade only in accordance with said predefined range of ignition timingrelationship to provide an optimum spark advance.
 2. In an engine havinga predetermined operating cycle and including wall means defining atleast one combustion chamber and igniting means associated with saidcombustion chamber for igniting a charge of fuel and air in saidcombustion chamber when energized, said fuel having a predeterminableoctane rating, an ignition system for controlling the timing of theignition of the charge for each of said combustion chamberscomprising;energizing means adapted to be connected to said ignitingmeans for energizing said igniting means in response to a timing signal,means for generating a timing signal operatively connected to saidenergizing means, said timing signal being adjustable with respect tothe mechanical cycle of each cylinder of said engine in response to anengine speed parameter and a charge density parameter, means forselecting an octane rating corresponding to said predeterminable octanerating, and means operatively connected to said timing signal generatingmeans for providing a predefined range of ignition timing relationshipsfor each of said combustion chambers in accordance with said selectedoctane rating, said engine speed parameter and said charge densityparameter, such that an ignition timing adjustment due to saidpredeterminable octane rating, said engine speed parameter and saidcharge density parameter is made only in accordance with said predefinedrange of ignition timing relationships on an individual basis for eachcombustion chamber of said engine.
 3. The system according to claim 1,wherein said manually adjustable octane selector comprises apotentiometer located within a passenger compartment of a vehicle. 4.The system according to claim 2, wherein said means for selecting anoctane rating comprises a potentiometer located within a passengercompartment of a vehicle.